Why You Feel Tired in the First Week of Keto
That initial burst of energy you were promised on the ketogenic diet might take a few days to arrive. In fact, you might feel quite the opposite to begin with. The ketogenic diet, which involves drastically reducing carbohydrate intake and replacing it with fat, forces your body to switch its primary fuel source. This transition can lead to fatigue.
The ‘Keto Flu’ Explained
The fatigue you experience during the first week of keto is often referred to as the ‘keto flu’. It’s not actually the flu, but rather a collection of symptoms that arise as your body adapts to using ketones for fuel instead of glucose. These symptoms can include:
- Fatigue and low energy
- Headaches
- Irritability
- Difficulty concentrating
- Muscle cramps
This cluster of symptoms arises because your body is used to running on glucose, which is readily available from carbohydrates. When you restrict carbs, your body has to learn to burn fat and produce ketones, a process that takes time and can be initially inefficient. This metabolic shift can temporarily disrupt your energy levels.
Electrolyte Imbalance
One of the main reasons for keto flu symptoms, including fatigue, is electrolyte imbalance. When you reduce carbohydrate intake, your insulin levels drop. This signals your kidneys to excrete more sodium and potassium. These are essential electrolytes that play a crucial role in energy production, nerve function, and fluid balance. As your body flushes out these electrolytes, you may experience fatigue, muscle weakness, and headaches. Learn more about replenishing electrolytes on keto.
Dehydration
Another factor contributing to fatigue during the first week of keto is dehydration. As your body excretes more sodium, it also loses more water. This can lead to dehydration, which can further exacerbate fatigue and other keto flu symptoms. Make sure you’re drinking plenty of water throughout the day, especially during the initial stages of the diet.
What this means in practice
To combat fatigue during the first week of keto, focus on staying hydrated by drinking plenty of water and supplementing with electrolytes. You can add a pinch of sea salt to your water or consume bone broth, which is rich in electrolytes. Many people find that supplementing with magnesium can also help reduce muscle cramps and fatigue. A magnesium citrate supplement from Boots costs around £7.00. Listen to your body and rest when you need to. Avoid strenuous activities until your body has fully adapted to using ketones for fuel. Read more about keto and exercise.
Frequently asked questions
Why does keto make me feel so tired?
When you cut carbs, your body switches from burning glucose to burning fat for fuel. This transition takes time, and your body may not be efficient at using ketones initially, leading to fatigue.
How long will the keto fatigue last?
The keto flu and associated fatigue typically last from a few days to a week. Once your body becomes more efficient at using ketones, your energy levels should stabilise.
How can I boost my energy on keto?
Ensure you’re getting enough electrolytes, staying hydrated, and consuming enough healthy fats. Adequate sleep and stress management can also help improve energy levels.
Should I stop keto if I feel too tired?
It’s normal to feel tired initially. However, if the fatigue is severe or persistent, consult with a healthcare professional to rule out any underlying issues.
The bottom line
Feeling tired during the first week of keto is a common experience caused by electrolyte imbalances, dehydration, and the metabolic shift to using ketones for fuel. By staying hydrated, supplementing with electrolytes, and getting enough rest, you can minimise these symptoms and ease the transition into ketosis. Remember that this fatigue is usually temporary and will subside as your body adapts. If you’d rather not do the macro maths yourself, the Keto Dieting app does it for you on Google Play and the App Store.
References
- Sumithran P, Prendergast LA, Delbridge E, et al. (2013). Ketosis and appetite-mediating nutrients and hormones after weight loss. European Journal of Clinical Nutrition. https://doi.org/10.1038/ejcn.2013.90
